Lower unit drain plug striped

[eriksat1]

1985 115 hp Merc outboard Lower unit drain / fill plug striped out. When it rains it pours. Can you install a helicoil without taking the parts out of the lower unit? I'm almost thinking of draining it good cleaning it up real good and JB Welding the plug back in, then fill with a squirt type oil can through the top vent screw hole. I would sure like to use the boat this weekend. Any other suggestions??

 

[Chris1956]

Re: Lower unit drain plug striped

Putting oil in the top will not work. Also you will not be able to drain it the next time. Merc used to sell an oversize plug that was installed and glued it. A smaller plug in the oversize one was then used to drain and fill. You might ask a Merc Dealer, as I have not seen them aftermarket.

 

[JB]

Re: Lower unit drain plug striped

You should be able to install a time-sert without dismantling the foot, Erik. That probably won't get you on the water tomorrow but it will turn your outboard back into a good, useful powerplant.

Be doubly sure to replace the gaskets under those plugs every time they are removed and to torque them only enough to crush the gaskets.

I don't trust helicoils to seal.

 

[eriksat1]

Re: Lower unit drain plug striped

Why can't you slowly fill it through the top hole? If you squirt the oil in slowly and measure the amount of oil you put in? It sure seems to come out of the top hole plenty fast. I realize it will have to vent the air out slowly, but I think it can be done? If I JB weld epoxy it and it holds / seals, I will deal with it next winter. If I epoxy it shut, I can always drill it out to drain it in the fall. The thing will be "IF" I can fill it through the top hole I guess. I have sealed up a lot of leaks before with JB Weld.

 

[chum1]

Re: Lower unit drain plug striped

This is one of those things that you might as well fix right the first time, jb weld/ epoxy wont cut it, why risk a lower end for the weekend what about the rest of the summer? I would personally try a helicoil kit from one of the auto stores to get it going if that doesnt work your screwed for the weekend or borrow someone elses boat

 

[eriksat1]

Re: Lower unit drain plug striped

I been doing a lot of searching and found this old post from 2007, sounds like maybe the best way to go. I never had much luck heli coiling lower unit drain plugs, they always either leaked or don't hold good, the thread depth is not good enough to hold a heli coil good. I'm think do as he says below but just tap the hole 1/8" pipe thread and use a stainless steel pipe plug the type with the female allen hex in it, and with a good coat of teflon pipe thread compound should seal it good.

From Scaaty 2007
"Been a Machinist all my life, but sometimes I can't figure why people give advice that is a "well, try this"., or whatever, without know the properties of all things metal. R. Johnson has one fix. What i would do is simply take some JB "WaterWeld" putty, fill the hole up and sand smooth (need a nice, oil free application). What threads are left will see it there for life. Somewhere in the same area (just above/below/side-tap the metal for a clear ring so you don't go into a bearing support-need to see the case myself to be sure) do a 1/4 drilled hole, drill stuck in grease to hold the chips. Now do a 1/4-3/8ths countersink and spot the case for the new o-ring or washer. re-drill (grease on everything again to hold chips), with a "F" drill, and re-tap 5/16th. Round head 5/16ths screw, oring,"